| 摘要 |
PURPOSE:To stabilize the density and gradation of a toner image, by setting the potential in the dark part of a V-D curve at a prescribed value in accordance with the measurement of the potential of a latent image, and controlling the inclination of the V-D curve in accordance with the measured density of the developed image. CONSTITUTION:A reference latent image is formed on a photoreceptor 1 by flickering of a blank exposing lamp after prescribed preparative operations upon turning on of a main switch. Both surface potentials in the bright and dark parts are measured alternately with a surface electrometer 7, and a primary electrostatic charger 3 is controlled to obtain the initially set surface potential. The standard white plate on the original plate is irradiated, and the quantity of the light of a lamp for illuminating the original is so controlled that the potential of the electrometer 7 attains 0V. The surface potential on the drum is measured and the potential for the DC component of a developing bias is determined. The potential for said DC component is applied on the drum to develop the latent image in the dark part and the density of the toner is measured with a detector 9 for reflection density, whereby the adequate surface potential in the dark part is determined. The similar control is successively accomplished in accordance with the surface potential determined in the above-mentioned way to control the height and inclination of the V-D curve, whereby the image having good density and gradation is obtd. |
